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WLAN, or Wireless Local Area Network, is a type of network that combines the benefits of wireless communication and computer networking. It uses wireless channels as its transmission medium to enable short-range wireless communication. Based on traditional wired LANs, WLAN allows wireless connectivity through devices like wireless access points (APs), wireless bridges, and network cards. This makes it easier to install, expand, and maintain compared to wired networks.
One of the key advantages of WLAN is its mobility, high speed, and use of open frequency bands. Enterprises, individuals, and service providers have recognized its value in wireless data transmission. It can be seamlessly integrated with Ethernet, allowing users to access the internet, perform online transactions, and work remotely. As applications grow, there are increasing demands for higher speed, better security, improved Quality of Service (QoS), and seamless roaming.
In addition to data transmission, WLAN is also expected to make progress in wireless voice applications. The following sections will explore current hot topics in WLAN development, including speed, security, QoS, roaming, and voice integration.
**Rate**
Bandwidth is the foundation of any wireless network. Most widely used WLAN devices operate under the 802.11b standard, which offers a maximum rate of 11 Mbps. However, due to overhead from headers and access control mechanisms, the actual user throughput is often around half of this. Devices based on 802.11a and 802.11g can reach up to 54 Mbps, but real-world performance is typically around 30 Mbps. The IEEE 802.11n working group is developing a faster standard, aiming to increase speeds to 108 Mbps or even 320 Mbps. Improvements in management and efficiency are also being explored to enhance overall performance.
**Security**
Since WLAN transmits data over wireless signals, it is inherently more vulnerable than wired networks. Any device within range can potentially intercept the signal. To address this, various security measures such as SSID, ACL, and WEP have been used. However, these are not always sufficient. The recent IEEE 802.11i standard introduces stronger security features, including Wi-Fi Protected Access (WPA) and Robust Security Network (RSN). WPA improves upon WEP by using TKIP encryption, which provides dynamic key updates. RSN, on the other hand, uses AES encryption for more secure data transmission and supports advanced authentication protocols.
**QoS**
Currently, WLAN follows an Ethernet-like sharing mechanism, making it difficult to differentiate between different types of traffic. This lack of prioritization can be problematic for applications like VoIP and video streaming, which require low latency and high bandwidth. To address this, the IEEE 802.11e task group has introduced mechanisms such as Enhanced Distributed Channel Access (EDCA) and Hybrid Coordination Function (HCF). These help prioritize traffic and ensure better quality of service for real-time applications.
**Roaming**
As users move between access points, maintaining a stable connection is crucial. The IEEE 802.11f protocol defines the Inter-Access Point Protocol (IAPP), which facilitates seamless roaming. It helps manage the extended service set (ESS) and ensures that each mobile device is connected to only one AP at a time, improving user experience and network stability.
**Voice Applications**
VoIP has become increasingly popular, and combining it with WLAN has led to the emergence of Voice over WLAN (VoWLAN). Wi-Fi-enabled phones are now available, though they are still limited to enterprise environments. Future developments may see them used in home and small office settings. Some manufacturers are also exploring dual-mode devices that combine WLAN with GSM or CDMA for broader coverage and flexibility.
**WiMAX: The New Wireless Metropolitan Area Network**
**Standard Situation**
The current WiMAX standard refers to the IEEE 802.16d standard, adopted in June 2004. It includes both the full version of IEEE 802.16 and 802.16a, covering both line-of-sight (LOS) and non-line-of-sight (NLOS) bands across a wide frequency range (2–66 GHz). WiMAX is also broadly understood as part of the IEEE 802.16 family of standards promoted by the WiMAX Forum.
**Advantages of WiMAX**
WiMAX combines the mobility and flexibility of Wi-Fi with the high bandwidth and reliable QoS of traditional broadband technologies like DSL and CableModem. Its most notable feature is the ability to support non-line-of-sight transmission, making it ideal for urban environments. It also offers flexible deployment, strong QoS support, and robust security features.
WiMAX uses dynamic adaptive modulation, enabling long-distance and obstacle-penetrating transmission. It can adjust bandwidth based on signal strength, ensuring stable connections. Operators can also scale their networks easily, dividing spectrum resources into multiple channels as needed.
WiMAX supports both enterprise and consumer services, including voice communications in remote areas. It also provides encryption and identity authentication to protect user data and meet enterprise security requirements.
**Application**
WiMAX is well-suited for last-mile broadband access, especially in areas where traditional broadband is not feasible. It can complement Wi-Fi hotspots and support wireless LANs in homes and small offices. The WiMAX Forum has outlined three main application categories: general IP, advanced IP, and non-IP services. These include web browsing, VoIP, video streaming, and SMS/MMS compatibility.
**Development Dynamics**
The WiMAX Forum is a non-profit organization with over 200 members, including equipment manufacturers, component suppliers, and service providers. Its goal is to ensure compatibility and interoperability among WiMAX devices. Similar to Wi-Fi and IEEE 802.11, the WiMAX Forum provides certification labels for tested products worldwide. It has established technical and certification working groups to develop future specifications and ensure quality testing.